The present invention relates to the field of paper manufacturing. More particularly, the present invention relates to the manufacture of absorbent tissue products such as bath tissue, facial tissue, napkins, towels, wipers, and the like. Specifically, the present invention relates to improved fabrics used to manufacture absorbent tissue products having visually discernible background texture regions bordered by curvilinear decorative elements, methods of tissue manufacture, methods of fabric manufacture, and the actual tissue products produced.
In the manufacture of tissue products, particularly absorbent tissue products, there is a continuing need to improve the physical properties and final product appearance. It is generally known in the manufacture of tissue products that there is an opportunity to mold a partially dewatered cellulosic web on a papermaking fabric specifically designed to enhance the finished paper product""s physical properties. Such molding can be applied by fabrics in an uncreped through air dried process as disclosed in U.S. Pat. No. 5,672,248 issued on Sep. 30, 1997 to Wendt et al., or in a wet pressed tissue manufacturing process as disclosed U.S. Pat. No. 4,637,859 issued on Jan. 20, 1987 to Trokhan. Wet molding typically imparts desirable physical properties independent of whether the tissue web is subsequently creped, or an uncreped tissue product is produced.
However, absorbent tissue products are frequently embossed in a subsequent operation after their manufacture on the paper machine, while the dried tissue web has a low moisture content, to impart consumer preferred visually appealing textures or decorative lines. Thus, absorbent tissue products having both desirable physical properties and pleasing visual appearances often require two manufacturing steps on two separate machines. Hence, there is a need to combine the generation of visually discernable background texture regions bordered by curvilinear decorative elements with the paper manufacturing process to reduce manufacturing costs. There is also a need to develop a paper manufacturing process that not only imparts visually discernable background texture regions bordered by curvilinear decorative elements to the sheet, but also maximizes desirable physical properties of the absorbent tissue products without deleteriously affecting other desirable physical properties.
Previous attempts to combine the above needs, such as those disclosed in U.S. Pat. No. 4,967,805 issued on Nov. 6, 1990 to Chiu, U.S. Pat. No. 5,328,565 issued on Jul. 12, 1994 to Rasch et al., and in U.S. Pat. No. 5,820,730 issued on Oct. 13, 1998 to Phan et al., have manipulated the papermaking fabric""s drainage in different localized regions to produce a pattern in the wet tissue web in the forming section of the paper machine. Thus, the texture results from more fiber accumulation in areas of the fabric having high drainage and fewer fibers in areas of the fabric having low drainage. Such a method can produce a dried tissue web having a non-uniform basis weight in the localized areas or regions arranged in a systematic manner to form the texture. While such a method can produce textures, the sacrifice in the uniformity of the dried tissue web""s physical properties such as tear, burst, absorbency, and density can degrade the dried tissue web""s performance while in use.
For the foregoing reasons, there is a need to generate aesthetically pleasing combinations of background texture regions and curvilinear decorative elements in the dried or partially dried tissue web, while being manufactured on the paper machine, using a method that produces a substantially uniform density dried tissue web which has improved performance while in use.
Numerous woven fabric designs are known in papermaking. Examples are provided by Sabut Adanur in Paper Machine Clothing, Lancaster, Pa.: Technomic Publishing, 1997, pp. 33-113, 139-148, 159-168, and 211-229. Another example is provided in Patent Application WO 00/63489, entitled xe2x80x9cPaper Machine Clothing and Tissue Paper Produced with Same,xe2x80x9d by H. J. Lamb, published on Oct. 26, 2000.
The problems experienced by those skilled in the art are overcome by the present invention which, in one aspect, comprises a tissue product having a substantially uniform density and first and second background regions having alternating ridges and depressions extending substantially parallel with the machine direction. A transition region is located between and separates the first and second background regions. In one embodiment of the present invention, the ridges within the first background region are offset from the ridges within the second background region and the depressions within the first background region are offset from the depressions within the second background region. The ridges and depressions within the first and second background regions can have a substantially uniform width or, in an alternative embodiment, the depressions can have a larger width than the ridges. The transition region can define any one of numerous decorative shapes and, in one aspect, can comprise curvilinear shapes.
The transition region can form a macroscopically different pattern, i.e. a visually distinctive pattern, by any one of various methods. As an example, the transition region can have a greater depth than the first and second background regions. As a further example, the transition region can have a height between that of the ridges and the depressions. As yet a further example, the transition region can comprise a gap having a length, in the machine direction, such as between 0.05 and 2 cm. Still further, the transition region can comprise an area wherein the offset ridges of adjacent first and second background regions overlap a certain distance such as, for example, between 0.05 and 1 cm. The transition region can have a curvilinear shape and, in a particular aspect, can surround the first back ground regions. The transition region, when surrounding the first background region, can form a discrete decorative element. The size of the decorative element can vary and, by way of example, can have a maximum dimension between 0.8 to 18 cm
In a further aspect of the present invention, a tissue product is provided comprising a sheet material having a three-dimensional texture and a substantially uniform density. The sheet material includes repeating first and second background regions separated by transitions regions. The first background regions and second background regions each include at least four raised elements or ridges per centimeter that extend in a direction substantially parallel to the machine direction of the sheet. The transition region is positioned between the first and second background regions and separates the two regions. In addition, the transition region has a pattern visually distinct from the pattern within the first and second background regions. The tissue sheet has excellent absorbency characteristics and, in one aspect, can have a z-directional wicking rate greater than 2 g/g/s. In other embodiments, the tissue sheet can have a z-directional wicking rate in excess of about 3 g/g/s. Desirably, the ridges within the first and/or second background regions are substantially uniformly spaced apart. Still more desirably, the first and second background regions have substantially uniformly spaced apart ridges and further have substantially the same number of ridges per centimeter. In this regard, in one embodiment of the present invention, the first and second background regions can each have between 5 and 10 ridges per cm. The transition region can vary in numerous respects such as, for example, those noted above. In a further aspect, the transition region can surround the first background region and define a decorative element. By way of example, the decorative element can have a length in the machine direction between about 1 and 18 cm.